The measure, which the Senate takes up Tuesday, would let insurers bypass coverage requirements mandated by states.

Supporters say that pre-empting the state requirements creates a trade-off that will help more businesses and their employers afford health insurance. Opponents say the bill would result in health insurance policies that don't protect workers when they get ill.

Under legislation sponsored by Sen. Mike Enzi, R-Wyo., businesses could band together based on their membership in a professional trade association to offer their workers scaled-back health insurance. Enzi predicts that most businesses will stick with the policies they currently offer rather than switch to a less comprehensive benefit.

However, many of the businesses that don't offer health insurance will find they can now afford to do so through the small business health plans. As a result, about 1 million currently uninsured workers would get coverage, he said.

"They have no insurance right now, so this would be an improvement," Enzi said.

The vote is expected to be close. The legislation pits business groups such as the National Federation of Independent Businesses, which supports the bill, against consumer groups, such as AARP and the American Cancer Society, which oppose it.

Sen. Chris Dodd, D-Conn., said he believes insurance companies will offer plans with minimal or no benefits, hoping to attract young and healthy people. Older, sicker people are going to be left without a plan that meets their needs.

"In one fell swoop, this bill will undo the work of each state to protect their citizens," Dodd said.

Insurers say the state mandates are driving up the cost of policies, and the ranks of the uninsured. States have approved more than 1,800 coverage requirements, says the Council for Affordable Health Insurance. For instance, mammograms are required in every state but Utah. In 31 states, insurers are required to cover child immunizations and annual exams.

But states also require coverage that opponents consider over-the-top. For instance, three states _ Connecticut, Minnesota and South Carolina _ require insurers to cover the evaluation and treatment of Lyme Disease. Seven states require insurers to cover wigs used for hair loss due to chemotherapy, says the council, which is funded by small insurance companies.

Other types of mandates occur as well. Some states recently increased the age at which insurers must cover unmarried dependents. In New Mexico, it's 25. In New Jersey, it's 30. Other states require insurers to accept anyone who applies, regardless of health status, the council said.

"Although one mandate may only increase the cost of a policy by 1 percent, 40 such mandates will price many people out of the market," the council said in a recent report.

The American Cancer Society said the cancer screenings that states require insurers to cover end up saving lives. The organization said, for example, that 11 states between 1999 and 2001 passed laws requiring insurers to cover the full range of colorectal screening tests. While screening has improved for those age 50-64 in all states, the rate of screening rose to 44.4 percent in states with coverage laws versus 41.8 percent in states without.

Forty-six states also require coverage for treatment and screening of diabetics, as well as the cost of their insulin.

"The need for diabetes care will not diminish simply because coverage shrinks," said Lawrence Smith, president of the American Diabetes Association. "Unfortunately, it will be our emergency rooms and Medicaid system that are forced to pay, thus overburdening an already strapped public health infrastructure."

Enzi's bill would let insurers bypass those requirements when offering and marketing insurance regionally and nationally. Insurers could offer the "basic plan" so long as they also offer an "enhanced plan." The enhanced plan must include benefits covered by the state employee health plan in one of the five most populous states _ California, Florida, Illinois, New York and Texas.

Enzi says small business owners often buy coverage that includes themselves as well as their employees.

"A small business owner who buys a skimpy policy is endangering more than just the morale in the workplace. He or she is jeopardizing morale around the dinner table," says a fact sheet released by Enzi's staff.

Democrats are expected to offer a competing bill Tuesday that also would allow small businesses to band together to purchase health insurance. The Office of Personnel Management would administer the benefit. The program would be set up like the Federal Employees Health Benefit Program, said the bill's sponsors, Sens. Dick Durbin, D-Ill., and Blanche Lincoln, D-Ark.

"If it's good enough for federal employees, and it's good enough for members of Congress, there's no reason we shouldn't use this model for small businesses and self-employed people," Lincoln said.